Proliferative Vitreoretinopathy (PVR) is characterized by proliferation of retinal pigment epithelial (RPE) cells, fibroblasts and glial cells in the periretinal space following trauma. The proliferation of these cells results in the formation of a membrane which causes puckering and/or retraction of the retina. PVR is the major complication arising from retinal re- attachment surgery. Polypeptide growth factors control the rate of proliferation in normal human cells in a paracrine manner. In proliferative diseases, endogenous production of and response to growth factors may lead to increased rates of cellular proliferation in an autocrine fashion. In appropriate production of polypeptide growth factors by RPE cells which migrate into the periretinal space in PVR could contribute to the pathology of this disease. Alternatively, the cells which proliferate in PVR could respond to growth factors normally present in the retina. Therefore, the specific aims of this project include: 1) The development of a defined serum-free medium for the growth of RPE cells in vitro; 2) Expanded studies on the production of growth factors by cultured RPE cells; 3) Determining whether growth factors produced by RPE cells can stimulate the proliferation of RPE cells and fibroblasts in vitro; 4) Histological examination of normal and pathological specimens to determine the distribution and synthesis of growth factors in the posterior chamber of the eye.